DESCRIPTION ( applicant's abstract): Our broad goal is to develop a four stage computational model of spatial vision, based on plausible physiological mechanisms, that predict the performance of normal foveal and peripheral vision, as well as the visual deficits associated with amblyopia. There is a great diversity of masking effects not handled by present models. One limitation of most current models is that they overlook retinal front-end effects and second order effects, such as texture processing. Another major limitation of current models is their reliance on fixed cortical spatial filters, followed by a primitive decision stage. Rather than inventing exotic spatial filters to account for unexplainable data, we suggest that a more parsimonious explanation, based on decision stage limits, can account for much of the data. The six aims of the proposal are organized into three categories: Modelfest: To enhance cross-fertilization among vision modelers, we have organized the Modelfest group. Modelfest is a new approach to modeling that involves the sharing of resources, learning from each other's success and providing a method to cross validate proposed models. Modelfest also facilitates interactions between vision science and medical imaging researchers, two groups with very different approaches to modeling. This interaction has already benefited us on decision stage issues. Our goal is to continue organizing, administering and promoting the group so that progress on vision modeling accelerates (Aim 1). Four-stage model: Current general purpose vision models virtually ignore several important stages of visual processing. We have developed several innovative methods to characterize processing at four stages, from early retinal processes to late decision stage variables. The proposed experiments will be used to define the computational model structure and to set the parameters at each stage. (Aims 2-5) Amblyopia and peripheral vision: Many of the stimuli used to develop the four stage model will also be used to test amblyopes and peripheral vision to determine the stages at which the peripheral and amblyopic visual systems differ from normal foveal vision. Wile past work has focused on early stage differences, there are now indications that some of the losses are taking place at later stages where information is integrated. The experimental results will be used to extend our model of spatial vision so that it predicts the visual losses associated with amblyopic and peripheral vision. (Aim 6)